Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
INF=10*10
H,W=map(int, input().split())
s=[list(input()) for _ in range(H)]
wall=sum(map(lambda x: x.count("#"), s))
d=[[INF for _ in range(W)] for _ in range(H)]
def bfs(h, w, c):
	if d[h][w] <= c:
		return
	d[h][w] = c
	for dh,dw in [(0, -1), (-1, 0), (0, 1), (1, 0)]:
		if h+dh >= 0 and w+dw >= 0 and h+dh < H and w+dw < W and s[h+dh][w+dw] == ".":
			bfs(h+dh, w+dw, c+1)
bfs(0, 0, 1)
print(-1 if d[H-1][W-1] == INF else H*W - d[H-1][W-1] - wall)